The Girls Aloud star, who worked with her fellow Geordie on The X Factor, said: “I would be devastated to see Joe lose possibly the best thing that could happen to him in his life. Every aspiring pop star dreams of a number one record.

“It is a beautiful song. He put his heart and soul into every single week of The X Factor and I cannot bear to see him lose out to a mean campaign that has nothing to do with his efforts.

“If that song, or should I say campaign, by an American group is our Christmas number one I’ll be gutted for him and our charts.”

Despite predictions that talent show winner McElderry would storm ahead when his CD went on sale on Wednesday, the rap-metal act were still in front last night.

The Climb had been available as a download since Monday, the day after McElderry’s victory over Olly Murs.

But the 18-year-old has narrowed the gap, with the difference between them now at around 40,000 copies.

Retailers and record company Sony will be rubbing their hands at the chart battle as the two tracks between them have now sold around 470,000 copies so far this week, according to Official Charts Company data.

If sales continue, they could sell upwards of 500,000 copies each by the weekend.

The last big Christmas battle anywhere near this scale was the Spice Girls’ Goodbye and South Park character Chef’s Chocolate Salty Balls in 1998. The Spice Girls won with 380,000 to their rival’s 375,000.

HMV spokesman Gennaro Castaldo said: “Whilst Joe remains behind in sales to date, the gap is clearly narrowing now that his CD single is out in the shops, and you’d have to say that the momentum lies with him – we think he will still do it, but it will be close.

“However, no-one could have predicted the Rage campaign against the X Factor would galvanise so much support, and it could easily keep growing now that its followers realise just how close they could be to causing one of the biggest upsets in UK charts history.”

Official Charts Company managing director Martin Talbot said: “The massive surge of interest in both of these records has set this up to be one of the biggest Christmas chart tussles many of us can remember.

“By the end of the week, we could be talking about more than one million sales across two singles in just a week, which is truly remarkable – and a tribute to the UK public’s love of the great British Christmas number one.”